INFORMATION PASTS IN GROUPS
A. V. Safonov · Mathematics of the USSR-Izvestiya · 1984
A simple algebraic characterization is obtained for information pasts in amenable groups. It is proved that a subset P of a countable amenable group G is an information past in G if and only if the set of negative elements for some linear ordering of G is invariant under left translations. Bibliography: 3 titles.